1. Field of the Invention
The invention relates to a method for manufacturing a sputtering target, more particularly to a method for manufacturing a sputtering target used in a film sputtering process.
2. Description of the Related Art
A hard disk drive is one of the media for storing data. The data is stored in a magnetic recording layer of the hard disk drive. The magnetic recording layer is primarily made of a cobalt-based alloy containing a precious metal (for example, platinum), and is formed on a substrate using a sputtering target by a sputtering process.
The sputtering process involves ion-bombarding the sputtering target using plasma, ejecting atoms from the surface of the target as a result of momentum transfer of the bombarding ions, and forming the magnetic recording layer on the substrate of the hard disk drive via adhesion, adsorption, surface-migration, and nucleation of the ejected atoms.
Since the manufacture of the hard disk drive involves specific technologies including electronic, semi-conductive, laser-optic, and precision machinery fields, the requirement for the sputtering target is relatively high. Therefore, the sputtering target can not be produced by a conventional atmospheric melt-casting process. Furthermore, since the sputtering target for forming the magnetic recording layer of the hard disk drive usually contains more than 30 wt % of precious metal (for example, platinum), it is desirable in the art to increase the yield of the precious metal in the sputtering target so as to avoid waste of the precious metal.
U.S. Pat. No. 6,797,137 discloses a target alloy, which is prepared by the following steps. Cobalt-chromium-boron master alloy powders are produced using conventional atomization or some other rapid solidification techniques. The master alloy powders are mechanically alloyed with platinum powders by ball milling. The resultant target alloy undergoes densification using a conventional hot isostatic pressing process to obtain the target alloy for the sputtering process for forming the magnetic recording layer of the hard disk drive. However, since it is not easy to obtain a homogeneous alloy by ball milling, the composition of the target alloy obtained thereby is not uniform, which may adversely affect the quality of the magnetic recording layer formed from the target alloy.
Taiwanese Patent No. I226907 discloses a method for preparing a sputtering target using a vacuum induction melting process and a vacuum arc remelting process so as to produce a highly pure cobalt-chromium alloy target. The vacuum arc remelting process is conducted in which an ingot produced by the vacuum induction melting process is used as a negative electrode and a copper crucible is used as a positive electrode so as to obtain a cast blank. However, since the ingot produced by the vacuum induction melting process has a shrinkage defect of more than 40%, the ingot should be trimmed prior to use as the negative electrode in the vacuum arc remelting process. Therefore, the yield of the sputtering target prepared by the method of the Taiwanese patent is usually lower than 60%.
Additionally, the equipments for performing the atomization process, the hot isostatic pressing process, the vacuum induction melting process, and the vacuum arc remelting process are relatively expensive. Therefore, the production cost of the prior art is relatively high.